It sounds to me like you might (accidentally) be paying for two separate accounts with one card. If you use this guide to check for another account, it is possible that you are paying for an account you don't know you have!
Once you've found an account and canceled its subscription -- or even if you can't find another account, just as long as you've checked -- let me know and I'll help you get in contact with Spotify support about fixing the extra payment 🙂
JacobRock Star 16
Help others find this answer and click "Accept as Solution".
If you appreciate my answer, maybe give me a Like.